Valentina Marin wore a purple T-shirt splattered with colored paint to school on Thursday.

It was a message against bullying and a sign of empathy she created herself.

“It represents how people feel when they are bullied,” she said. “Their feelings are all over the place.”

Marin, 12, of Flanders, was joined by many of her classmates at Riverhead Middle School who designed T-shirts with anti-bullying messages in recognition of National Youth Violence Prevention Week. Students at Riverhead Middle School participated by placing purple ribbons on their lockers this week, taking surveys about what it means to be a bully and holding a day of silence on Wednesday.

The week of activities was designed by Denise DeMattia, an intern working in the middle school guidance department as she finishes classes for a master's degree in mental health counseling at Long Island University.

DeMattia, 28, said she was bullied when she was in school so it was important to her to share the initiative with the students in Riverhead. When a group of students approached her about a bullying video they had seen on YouTube, she coordinated with national awareness week and developed a series of activities the students could do that wouldn’t take them out of class.

She said the bullying surveys and the day of silence have seemed to have the most impact on the students. The survey, passed out in classes on Monday morning, described the behavior of a bully.

“It really got students thinking about what is acceptable and what is not acceptable,” she said.

On Wednesday, 165 of the school’s roughly 700 students participated in a day of silence. The gesture was a show of support to students who have been bullied but remained silent about it.

Marin said she thought the day of silence was the most effective activity because it gave people the opportunity to think about everything they had learned about bullying.

“My friend on the bus this morning said, ‘Oh, last night I was thinking about how bullies must feel, so I’m going to start being nice,’ ” she said.

Jennifer Berzolla, the middle school guidance counselor who supervises DeMattia, said the school is a “close-knit and caring” one, but bullying happens. She said the most important message for the students that week was to speak out when they see bad behavior or are being bullied themselves.

She said she thinks that message has gotten across.

“I just feel it,” she said. “I just see the way the kids are acting around each other.”

Molly Fritscher, 12, of Calverton, said she’s been bullied since the second grade. She said she was excited to hear about the week’s events because she thought it would send an important message. She said she thought the day of silence had an impact because it showed people what it felt like to be forced into silence through bullying.

After the day of silence, a girl who usually ignores her started talking to her.

“Now I feel like everybody could be nicer,” she said. “I feel like it could change.”